From Tips and Stepsconcrete involves many steps to achieve the best results, including forming, grading, placing, and finishing. One critical step is placing the reinforcing bars, or rebar correctly, and this article will explain how this is done.
- Plan the project. For structural concrete construction, an engineer and architect will usually do the technical design work and provide specific information regarding the sizes, configuration, and placement of rebar in the associated concrete work. Planning the actual fabrication and placement, as well as the schedule of the work is your first task.
- Corner bars. These are also L shapes, with each side of the ell the same length.
- Offset bends. These range from a simple Z shape to complex angles, used in reinforcing concrete walkway steps and steps (changes in elevation) in concrete footings.
- Hairpins. These are U shaped rebar that are often used to interlock two or more individual mats of rebar to give lateral strength to the concrete casting.
- Consult your reinforcing placement drawings/plan. If you purchase your rebar from a fabricator, the supplier will usually review your structural engineer's or architect's plans and produce a shop drawing with details and identifying tags for each type of rebar used in the project. For simpler projects, your building plans should provide spacing requirements and bar sizes. Use these documents to determine where and what rebar is needed in individual locations.
- excavations, and underground rough ins for plumbing and electrical utilities is finished. Lay out the actual perimeter or form lines for the concrete placement after the grading and compaction and associated testing is done.
- Figure 8 ties. These are made by pulling the wire around the rear (from the rodbuster) bar, diagonally across the front bar, back around the rear bar, diagonally in the opposite direction across the front bar, and then twisting back around the beginning wire. You then cut the wire feeding off the reel, and bend the cut ends back towards the tie so no sharp ends project from the tie. These ties will help hold perpendicular bars tightly together while helping to prevent them from racking, or moving diagonally.
- Saddle ties. Similar to the figure 8 tie, you begin by passing the wire feeding from your reel behind the rear bar, then across the front bar staying parallel to the bar. You then pass it behind the rear bar again, back around the front bar on the opposite side. You now twist the ends together, cut the feed wire, and bend the cut ends back. This tie is often used when tying rebar for walls or other vertical application where the rodbuster will actually climb on the rebar framework to access higher portions of the wall. The figure 8 and saddle tie can often be interchanged, however, technically speaking, there are advantages to each one in certain circumstances.
- Combinations of figure 8 and saddle ties with additional wraps around vertical rebars can be used to increase the hold of the tie so bars cannot slip downward when weight is applied to them or the plastic concrete is dropped into the form.
- Bulkhead dowels. In instances where a footing will not be completed in a single concrete placement, you will need to dowel out of the bulkhead form so the next placement will be structurally tied to the latter one. Make sure the dowels extend far enough that the lateral reinforcement will overlap enough to maintain the strength of the rods used. Typically, rebar lap is calculated in bar diameters. An example would be the number 5 rebar mentioned earlier. It has a diameter of 5/8 of an inch, and the required lap might be 40 bar diameters. Mulitplying the diameter 5/8 by 40, you will get 200/8, or 25 inches.
- Keep rebar stored on dunnage to prevent rusting, and to keep bars from becoming buried in soft soils. Any build up of iron oxide (rust) will exacerbate spalling later on.
- Buy quality tools if you plan to do a lot of rebar tying. Cheap wire reels and pliers won't hold up to the wear and tear of daily use.
- Double check the rebar placement drawings, especially for dowels, since misplaced dowels must be cut off, and new ones epoxied in the correct location, at considerable expense.
- Wear the correct safety equipment for this work. Gloves are especially important to protect the rodbuster's hands.
- Rebar ends and the ends of cut tie wire can be incredibly sharp.
- Impalement protection caps are required by law in the United States.
Things You'll Need
- Rebar and a rebar placement plan.
- Pliers or a Snap Tie spinner.
- Wire and a wire reel.
- Marking crayons, soapstone, or paint.
- Tape measure.
Related Tips and Steps
- How to Build a Straight Form for Concrete
- How to Finish Concrete
- How to Finish a Large Span of Concrete
From Wikihow Tie Rebar